linux-kernel - [PATCH v3 3/3] PCI/sysfs: Prohibit unaligned access to I/O port on non-x86

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Message-ID: <20260108015944.3520719-4-duziming2@huawei.com>
Date: Thu, 8 Jan 2026 09:59:44 +0800
From: Ziming Du <duziming2@...wei.com>
To: <bhelgaas@...gle.com>
CC: <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<liuyongqiang13@...wei.com>, <duziming2@...wei.com>
Subject: [PATCH v3 3/3] PCI/sysfs: Prohibit unaligned access to I/O port on non-x86

From: Yongqiang Liu <liuyongqiang13@...wei.com>

Unaligned access is harmful for non-x86 archs such as arm64. When we
use pwrite or pread to access the I/O port resources with unaligned
offset, system will crash as follows:

Unable to handle kernel paging request at virtual address fffffbfffe8010c1
Internal error: Oops: 0000000096000061 [#1] SMP
Call trace:
 _outw include/asm-generic/io.h:594 [inline]
 logic_outw+0x54/0x218 lib/logic_pio.c:305
 pci_resource_io drivers/pci/pci-sysfs.c:1157 [inline]
 pci_write_resource_io drivers/pci/pci-sysfs.c:1191 [inline]
 pci_write_resource_io+0x208/0x260 drivers/pci/pci-sysfs.c:1181
 sysfs_kf_bin_write+0x188/0x210 fs/sysfs/file.c:158
 kernfs_fop_write_iter+0x2e8/0x4b0 fs/kernfs/file.c:338
 vfs_write+0x7bc/0xac8 fs/read_write.c:586
 ksys_write+0x12c/0x270 fs/read_write.c:639
 __arm64_sys_write+0x78/0xb8 fs/read_write.c:648

Powerpc seems affected as well, so prohibit the unaligned access
on non-x86 archs.

Fixes: 8633328be242 ("PCI: Allow read/write access to sysfs I/O port resources")
Signed-off-by: Yongqiang Liu <liuyongqiang13@...wei.com>
Signed-off-by: Ziming Du <duziming2@...wei.com>
---
 drivers/pci/pci-sysfs.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 7e697b82c5e1..11d8b7ec4263 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -31,6 +31,7 @@
 #include <linux/of.h>
 #include <linux/aperture.h>
 #include <linux/unaligned.h>
+#include <linux/align.h>
 #include "pci.h"
 
 #ifndef ARCH_PCI_DEV_GROUPS
@@ -1166,12 +1167,20 @@ static ssize_t pci_resource_io(struct file *filp, struct kobject *kobj,
 			*(u8 *)buf = inb(port);
 		return 1;
 	case 2:
+		#if !defined(CONFIG_X86)
+			if (!IS_ALIGNED(port, count))
+				return -EFAULT;
+		#endif
 		if (write)
 			outw(*(u16 *)buf, port);
 		else
 			*(u16 *)buf = inw(port);
 		return 2;
 	case 4:
+		#if !defined(CONFIG_X86)
+			if (!IS_ALIGNED(port, count))
+				return -EFAULT;
+		#endif
 		if (write)
 			outl(*(u32 *)buf, port);
 		else
-- 
2.43.0